Thermal Properties of Selected Group of Dental Materials

Mini Review

J Dent App. 2023; 9(1): 1119.

Thermal Properties of Selected Group of Dental Materials

Borut Kosec¹*; Mateja Vodlan²; Aleš Nagode¹; Alenka Pavlič³; Igor Kopač³; Matija Zorc¹; Hennry Taubmann4; Igor Budak5; Tatjana Puškar6; Blaž Karpe¹

1University of Ljubljana, Faculty of Natural Sciences and Engineering, Aškerčeva 12, 1000 Ljubljana, Slovenia

2LEK d.d., Verovskova 57, 1526 Ljubljana, Slovena

3University of Ljubljana, Faculty of Medicine, Korytkova 2, 1000 Ljubljana, Slovenia,

4C3 Prozess und Analysentechnik Gmbh, Peter Henlein Str. 20, Munich, Germany

5University of Novi Sad, Faculty Technical Sciences, Trg D. Obradovica 6, 21000 Novi Sad, Serbia

6University of Novi Sad, Faculty of Medicine, Hajduk Veljkova 6, 21000 Novi Sad, Serbia

*Corresponding author: Borut Kosec University of Ljubljana, Faculty of Natural Sciences and Engineering, Aškerčeva 12, 1000 Ljubljana, Slovenia. Phone: +386 1 2000410, Fax: +386 1 4704560 Email: borut.kosec@ntf.uni-lj.si

Received: April 17, 2023 Accepted: May 11, 2023 Published: May 18, 2023

Abstract

The thermal properties of dentine and tooth enamel affects the rate of response of the tooth nervous system to the temperature changes to which the tooth is exposed on a daily basis.

Today almost all manufacturers of dental materials in their certificates of material quality describe material chemical composition, mechanical properties, process ability and aesthetic characteristics, while information about thermal properties (thermal conductivity, thermal capacity and temperature diffusivity) are not available.

Within the interdisciplinary teamwork, thermal properties of five selected dental materials were measured and analyzed by modern Transient Plane Source (TPS) method in accordance with the standard ISO 22007-2. Thermal properties were measured at temperature interval between 0°C and 50°C.

Keywords: Dental materials; Thermal properties; TPS: Transient plane source; Method; Measurement

Introduction

The thermal properties of dentine and tooth enamel affects the rate of response of the tooth nervous system to the temperature changes to which the tooth is exposed on a daily basis. In addition to strength and aesthetic requirements, artificial dental materials must also provide a similar thermal protection for the tooth pulp. Likewise, implants and artificial tooth crowns must transfer similar heat flow to the bone as is transferred by a natural tooth, which has a strong influence on the patient's general acceptance of the foreign body [1,2].

Manufacturers of dental materials in their certificates of material quality describe chemical composition, mechanical properties, machinability and aesthetic characteristics, while thermal properties of the material are rarely given [3].

The reported values of human teeth thermal properties show significant discrepancies, with data for thermal conductivity of dentine between 0.11 to 0.98 Wm-1 K-1, and 0.7 to 0.8 Wm-1 K-1 for tooth enamel, while temperature diffusivity varies between 0.058 to 0.269mm²/s and 0.092 to 0.42 mm²/s for dentin and enamel respectively. The significant discrepancy between the reported results may be attributed to several challenges associated with the measurements, like tooth heterogeneous microstructure and associative anisotropic thermal properties, difficulties at establishing suitable thermal contact or lack of precise emissivity data when axial heat flow or laser flash measuring methods are applied [4].

Thermal Properties Measurement

Thermal conductivity, specific heat and thermal diffusivity are basic thermal properties of material that determine the heat transfer in the system under consideration. Despite the remarkable progress of measuring methods and techniques, it is still difficult to determine them with an error of less than ±2%, even for bulk materials.

In our research, we used one of the most advanced instruments for measuring the thermal properties, Hot Disk TPS 2200, a product of Hot Disk AB company, Gothenburg, Sweden [5]. The instrument can be used for determining thermal properties of various materials including pure metals, alloys, minerals, ceramics, plastics, glasses, powders and viscous liquids with thermal conductivity in the range from 0.01 to 500 W/mK, thermal diffusivity from 0.01 to 300mm2/s and heat capacity up to 5 MJ/m³K. Measurements can be performed in a temperature interval between -0 up to 750°C [6].

Hot disk measuring method is a Transient Plane Source (TPS) technique. Based on the theory of TPS, instrument utilizes a sensor element in the shape of 10μm thick double spiral, made by etching from pure nickel foil. Spiral is mechanically strengthen and electrically insulated on both sides by thin polyimide foil (Kapton ®Du Pont) for measurements up to 300°C or mica foil for measurements up to 750°C. Sensor acts both as a precise heat source and resistance thermometer for recording the time dependent temperature increase (Figure 1).